[RFC PATCH 05/14] memcg: Add mem_cgroup_uncharge_folios()

["Matthew Wilcox (Oracle)" <willy@infradead.org>]

Almost identical to mem_cgroup_uncharge_list(), except it takes a
folio_batch instead of a list_head.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 include/linux/memcontrol.h | 12 ++++++++++++
 mm/memcontrol.c            | 13 +++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index ab94ad4597d0..d0caeb1c1136 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -713,6 +713,14 @@ static inline void mem_cgroup_uncharge_list(struct list_head *page_list)
 	__mem_cgroup_uncharge_list(page_list);
 }
 
+void __mem_cgroup_uncharge_folios(struct folio_batch *folios);
+static inline void mem_cgroup_uncharge_folios(struct folio_batch *folios)
+{
+	if (mem_cgroup_disabled())
+		return;
+	__mem_cgroup_uncharge_folios(folios);
+}
+
 void mem_cgroup_migrate(struct folio *old, struct folio *new);
 
 /**
@@ -1273,6 +1281,10 @@ static inline void mem_cgroup_uncharge_list(struct list_head *page_list)
 {
 }
 
+static inline void mem_cgroup_uncharge_folios(struct folio_batch *folios)
+{
+}
+
 static inline void mem_cgroup_migrate(struct folio *old, struct folio *new)
 {
 }
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 26ba9d1a66d1..a0fb008afa23 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -33,6 +33,7 @@
 #include <linux/shmem_fs.h>
 #include <linux/hugetlb.h>
 #include <linux/pagemap.h>
+#include <linux/pagevec.h>
 #include <linux/vm_event_item.h>
 #include <linux/smp.h>
 #include <linux/page-flags.h>
@@ -7190,6 +7191,18 @@ void __mem_cgroup_uncharge_list(struct list_head *page_list)
 		uncharge_batch(&ug);
 }
 
+void __mem_cgroup_uncharge_folios(struct folio_batch *folios)
+{
+	struct uncharge_gather ug;
+	unsigned int i;
+
+	uncharge_gather_clear(&ug);
+	for (i = 0; i < folios->nr; i++)
+		uncharge_folio(folios->folios[i], &ug);
+	if (ug.memcg)
+		uncharge_batch(&ug);
+}
+
 /**
  * mem_cgroup_migrate - Charge a folio's replacement.
  * @old: Currently circulating folio.
-- 
2.40.1